通过组合导航传递 Parcelable 参数

Question

I want to pass a parcelable object ( BluetoothDevice ) to a composable using compose navigation.

Passing primitive types is easy:

composable(
  "profile/{userId}",
  arguments = listOf(navArgument("userId") { type = NavType.StringType })
) {...}

navController.navigate("profile/user1234")

But I can't pass a parcelable object in the route unless I can serialize it to a string.

composable(
  "deviceDetails/{device}",
  arguments = listOf(navArgument("device") { type = NavType.ParcelableType(BluetoothDevice::class.java) })
) {...}

val device: BluetoothDevice = ...
navController.navigate("deviceDetails/$device")

The code above obviously doesn't work because it just implicitly calls toString() .

Is there a way to either serialize a Parcelable to a String so I can pass it in the route or pass the navigation argument as an object with a function other than navigate(route: String) ?

Answer 1

Warning: Ian Lake is an Android Developer Advocate and he says in this answer that pass complex data structures is an anti-pattern (referring the documentation). He works on this library, so he has authority on this. Use the approach below by your own.

Edit: Updated to Compose Navigation 2.4.0-beta07

Seems like previous solution is not supported anymore. Now you need to create a custom NavType .

Let's say you have a class like:

@Parcelize
data class Device(val id: String, val name: String) : Parcelable

Then you need to define a NavType

class AssetParamType : NavType<Device>(isNullableAllowed = false) {
    override fun get(bundle: Bundle, key: String): Device? {
        return bundle.getParcelable(key)
    }

    override fun parseValue(value: String): Device {
        return Gson().fromJson(value, Device::class.java)
    }

    override fun put(bundle: Bundle, key: String, value: Device) {
        bundle.putParcelable(key, value)
    }
}

Notice that I'm using Gson to convert the object to a JSON string. But you can use the conversor that you prefer...

Then declare your composable like this:

NavHost(...) {
    composable("home") {
        Home(
            onClick = {
                 val device = Device("1", "My device")
                 val json = Uri.encode(Gson().toJson(device))
                 navController.navigate("details/$json")
            }
        )
    }
    composable(
        "details/{device}",
        arguments = listOf(
            navArgument("device") {
                type = AssetParamType()
            }
        )
    ) {
        val device = it.arguments?.getParcelable<Device>("device")
        Details(device)
    }
}

Original answer

Basically you can do the following:

// In the source screen...
navController.currentBackStackEntry?.arguments = 
    Bundle().apply {
        putParcelable("bt_device", device)
    }
navController.navigate("deviceDetails")

And in the details screen...

val device = navController.previousBackStackEntry
    ?.arguments?.getParcelable<BluetoothDevice>("bt_device")

Answer 2

I've written a small extension for the NavController.

import android.os.Bundle
import androidx.core.net.toUri
import androidx.navigation.*

fun NavController.navigate(
    route: String,
    args: Bundle,
    navOptions: NavOptions? = null,
    navigatorExtras: Navigator.Extras? = null
) {
    val routeLink = NavDeepLinkRequest
        .Builder
        .fromUri(NavDestination.createRoute(route).toUri())
        .build()

    val deepLinkMatch = graph.matchDeepLink(routeLink)
    if (deepLinkMatch != null) {
        val destination = deepLinkMatch.destination
        val id = destination.id
        navigate(id, args, navOptions, navigatorExtras)
    } else {
        navigate(route, navOptions, navigatorExtras)
    }
}

As you can check there are at least 16 functions " navigate " with different parameters, so it's just a converter for use

public open fun navigate(@IdRes resId: Int, args: Bundle?) 

So using this extension you can use Compose Navigation without these terrible deep link parameters for arguments at routes.

Answer 3

Here's my version of using the BackStackEntry

Usage:

composable("your_route") { entry ->
    AwesomeScreen(entry.requiredArg("your_arg_key"))
}
navController.navigate("your_route", "your_arg_key" to yourArg)

Extensions:

fun NavController.navigate(route: String, vararg args: Pair<String, Parcelable>) {
    navigate(route)
    
    requireNotNull(currentBackStackEntry?.arguments).apply {
        args.forEach { (key: String, arg: Parcelable) ->
            putParcelable(key, arg)
        }
    }
}

inline fun <reified T : Parcelable> NavBackStackEntry.requiredArg(key: String): T {
    return requireNotNull(arguments) { "arguments bundle is null" }.run {
        requireNotNull(getParcelable(key)) { "argument for $key is null" }
    }
}

Answer 4

The backStackEntry solution given by @nglauber will not work if we pop up ( popUpTo(...) ) back stacks on navigate(...) .

So here is another solution. We can pass the object by converting it to a JSON string.

Example code:

val ROUTE_USER_DETAILS = "user-details?user={user}"


// Pass data (I am using Moshi here)
val user = User(id = 1, name = "John Doe") // User is a data class.

val moshi = Moshi.Builder().build()
val jsonAdapter = moshi.adapter(User::class.java).lenient()
val userJson = jsonAdapter.toJson(user)

navController.navigate(
    ROUTE_USER_DETAILS.replace("{user}", userJson)
)


// Receive Data
NavHost {
    composable(ROUTE_USER_DETAILS) { backStackEntry ->
        val userJson =  backStackEntry.arguments?.getString("user")
        val moshi = Moshi.Builder().build()
        val jsonAdapter = moshi.adapter(User::class.java).lenient()
        val userObject = jsonAdapter.fromJson(userJson)

        UserDetailsView(userObject) // Here UserDetailsView is a composable.
    }
}


// Composable function/view
@Composable
fun UserDetailsView(
    user: User
){
    // ...
}

Answer 5

Here is another solution that works also by adding the Parcelable to the correct NavBackStackEntry , NOT the previous entry . The idea is first to call navController.navigate , then add the argument to the last NavBackStackEntry.arguments in the NavController.backQueue . Be mindful that this does use another library group restricted API (annotated with RestrictTo(LIBRARY_GROUP) ), so could potentially break. Solutions posted by some others use the restricted NavBackStackEntry.arguments , however NavController.backQueue is also restricted.

Here are some extensions for the NavController for navigating and NavBackStackEntry for retrieving the arguments within the route composable:

fun NavController.navigate(
    route: String,
    navOptions: NavOptions? = null,
    navigatorExtras: Navigator.Extras? = null,
    args: List<Pair<String, Parcelable>>? = null,
) {
    if (args == null || args.isEmpty()) {
        navigate(route, navOptions, navigatorExtras)
        return
    }
    navigate(route, navOptions, navigatorExtras)
    val addedEntry: NavBackStackEntry = backQueue.last()
    val argumentBundle: Bundle = addedEntry.arguments ?: Bundle().also {
        addedEntry.arguments = it
    }
    args.forEach { (key, arg) ->
        argumentBundle.putParcelable(key, arg)
    }
}

inline fun <reified T : Parcelable> NavController.navigate(
    route: String,
    navOptions: NavOptions? = null,
    navigatorExtras: Navigator.Extras? = null,
    arg: T? = null,
    
) {
    if (arg == null) {
        navigate(route, navOptions, navigatorExtras)
        return
    }
    navigate(
        route = route,
        navOptions = navOptions,
        navigatorExtras = navigatorExtras,
        args = listOf(T::class.qualifiedName!! to arg),
    )
}

fun NavBackStackEntry.requiredArguments(): Bundle = arguments ?: throw IllegalStateException("Arguments were expected, but none were provided!")

@Composable
inline fun <reified T : Parcelable> NavBackStackEntry.rememberRequiredArgument(
    key: String = T::class.qualifiedName!!,
): T = remember {
    requiredArguments().getParcelable<T>(key) ?: throw IllegalStateException("Expected argument with key: $key of type: ${T::class.qualifiedName!!}")
}

@Composable
inline fun <reified T : Parcelable> NavBackStackEntry.rememberArgument(
    key: String = T::class.qualifiedName!!,
): T? = remember {
    arguments?.getParcelable(key)
}

To navigate with a single argument, you can now do this in the scope of a NavGraphBuilder :

composable(route = "screen_1") {
    Button(
        onClick = {
            navController.navigate(
                route = "screen_2",
                arg = MyParcelableArgument(whatever = "whatever"),
            )
        }
    ) {
        Text("goto screen 2")
    }
}
composable(route = "screen_2") { entry ->
    val arg: MyParcelableArgument = entry.rememberRequiredArgument()
    // TODO: do something with arg
}

Or if you want to pass multiple arguments of the same type:

composable(route = "screen_1") {
    Button(
        onClick = {
            navController.navigate(
                route = "screen_2",
                args = listOf(
                    "arg_1" to MyParcelableArgument(whatever = "whatever"),
                    "arg_2" to MyParcelableArgument(whatever = "whatever"),
                ),
            )
        }
    ) {
        Text("goto screen 2")
    }
}
composable(route = "screen_2") { entry ->
    val arg1: MyParcelableArgument = entry.rememberRequiredArgument(key = "arg_1")
    val arg2: MyParcelableArgument = entry.rememberRequiredArgument(key = "arg_2")
    // TODO: do something with args
}

The key benefit of this approach is that similar to the answer that uses Moshi to serialise the argument, it will work when popUpTo is used in the navOptions , but will also be more efficient as no JSON serialisation is involved.

This will of course not work with deep links, but it will survive process or activity recreation. For cases where you need to support deep links or even just optional arguments to navigation routes, you can use the entry.rememberArgument extension. Unlike entry.rememberRequiredArgument , it will return null instead of throwing an IllegalStateException .

Answer 6

Following nglauber suggestion, I've created two extensions which are helping me a bit

@Suppress("UNCHECKED_CAST")
fun <T> NavHostController.getArgument(name: String): T {
    return previousBackStackEntry?.arguments?.getSerializable(name) as? T
        ?: throw IllegalArgumentException()
}

fun NavHostController.putArgument(name: String, arg: Serializable?) {
    currentBackStackEntry?.arguments?.putSerializable(name, arg)
}

And I use them this way:

Source:
navController.putArgument(NavigationScreens.Pdp.Args.game, game)
navController.navigate(NavigationScreens.Pdp.route)

Destination:
val game = navController.getArgument<Game>(NavigationScreens.Pdp.Args.game)
PdpScreen(game)

Answer 7

you can pass an argument like this

val data = DetailScreenArgument(title = "Sample")

navController.currentBackStackEntry?.savedStateHandle?.apply {
   set("detailArgument", data)
}

navController.navigate(Screen.DetailScreen.route)

and get the argument in the destination like this

val detailArgument = navController.previousBackStackEntry?.savedStateHandle?.get<DetailScreenArgument>(
    "detailArgument"
)

Answer 8

You can use my own solution: https://github.com/usmonie/compose_navigation_with_parcelable_arguments

With my solution, you will be able to get parcelable values directly into the composable function

Answer 9

I get a weird bug when I implement the top answer to this question. Like I have the following Parcelable to pass between two screens of my Jetpack Compose app:

@Parcelize
data class EdgeParcelable(
    val node: NodeParcelable?,
    val cursor: String?,
) : Parcelable

And as the accepted Answer says I have implemented a custom NavType:

class EdgeParcelableType : NavType<EdgeParcelable>(isNullableAllowed = false) {

    override val name: String
        get() = "edge"

    override fun get(bundle: Bundle, key: String): EdgeParcelable? {
        return bundle.getParcelable(key)
    }

    override fun parseValue(value: String): EdgeParcelable {
        return Gson().fromJson(value, EdgeParcelable::class.java)
    }

    override fun put(bundle: Bundle, key: String, value: EdgeParcelable) {
        bundle.putParcelable(key, value)
    }
}

And in my Composable function where I create the NavHost I have:

@Composable
fun MyApp(viewModel: MyViewModel, modifier: Modifier = Modifier) {
    val navController = rememberNavController()
    Scaffold(
        modifier = modifier.fillMaxSize(),
        topBar = { MyTopAppBar(
            currentScreen=currentScreen,
            canNavigateBack = navController.previousBackStackEntry != null,
            navigateUp = { navController.navigateUp() }
        ) }
    ) { innerPadding ->
        NavHost(
            navController = navController,
            startDestination = "home",
            modifier = Modifier.padding(innerPadding)
        ) {
            composable(route = "home") {
                val lazyPagingItems = viewModel.Items()
                HomeScreen(
                    lazyPagingItems = lazyPagingItems,
                    onTownClicked = { edge: EdgeParcelable ->
                        val json = Uri.encode(Gson().toJson(edgeParcelable))
                      
                     navController.navigateSingleTopTo("hotspots/$json")
                    },
                    modifier = ...
                )
            }
            composable(
                route = "hotspots/{edge}",
                arguments = listOf(
                    navArgument("edge") {
                        type = EdgeParcelableType()
                    }
                )
            ) {
                val edgeParcelable = it.arguments?.getParcelable<EdgeParcelable>("edge")
                HotspotsScreen(edgeParcelable)
            }
        }
    }
}

The code above crashes my Application when I add the lines:

val bsEntry by navController.currentBackStackEntryAsState()
val currentScreen = bsEntry?.destination?.route ?: "Home"

Adding the above lines make the Composable become:

@Composable
fun MyApp(viewModel: MyViewModel, modifier: Modifier = Modifier) {
    val navController = rememberNavController()

    // Adding these causes a problem...
    val bsEntry by navController.currentBackStackEntryAsState()
    val currentScreen = bsEntry?.destination?.route ?: "Home"

    Scaffold(
        modifier = modifier.fillMaxSize(),
        topBar = { MyTopAppBar(
            currentScreen=currentScreen,
            canNavigateBack = navController.previousBackStackEntry != null,
            navigateUp = { navController.navigateUp() }
        ) }
    ) { innerPadding ->
        NavHost(
            navController = navController,
            startDestination = "home",
            modifier = Modifier.padding(innerPadding)
        ) {
            composable(route = "home") {
                val lazyPagingItems = viewModel.Items()
                HomeScreen(
                    lazyPagingItems = lazyPagingItems,
                    onTownClicked = { edge: EdgeParcelable ->
                        val json = Uri.encode(Gson().toJson(edgeParcelable))
                     navController.navigateSingleTopTo("hotspots/$json")
                    },
                    modifier = ...
                )
            }
            composable(
                route = "hotspots/{edge}",
                arguments = listOf(
                    navArgument("edge") {
                        type = EdgeParcelableType()
                    }
                )
            ) {
                val edgeParcelable = it.arguments?.getParcelable<EdgeParcelable>("edge")
                HotspotsScreen(edgeParcelable)
            }
        }
    }
}

Passing my Custom NavType with the following line of code:

arguments = listOf(navArgument("edge") { type = EdgeParcelableType() } )

now crashes my app, by rendering it unusable. The app seems to choke on itself, almost like, the Navigation API does not really understand the new Custom EdgeParcleableType() or perhaps something is missing that remains to be added to make this EdgeParcelableType work well with the Navigation API.

I was only able to solve the problem by changing the type above to StringType as follows:

arguments = listOf( navArgument("edge") { type = NavType.StringType }

And passing around strings in the rest of the Composable as follows:

@Composable
fun MyApp(viewModel: MyViewModel, modifier: Modifier = Modifier) {
    val navController = rememberNavController()

    // Using NavType.StringType allows this work...
    val bsEntry by navController.currentBackStackEntryAsState()
    val currentScreen = bsEntry?.destination?.route ?: "Home"

    Scaffold(
        modifier = modifier.fillMaxSize(),
        topBar = { MyTopAppBar(
            currentScreen=currentScreen,
            canNavigateBack = navController.previousBackStackEntry != null,
            navigateUp = { navController.navigateUp() }
        ) }
    ) { innerPadding ->
        NavHost(
            navController = navController,
            startDestination = "home",
            modifier = Modifier.padding(innerPadding)
        ) {
            composable(route = "home") {
                val lazyPagingItems = viewModel.Items()
                HomeScreen(
                    lazyPagingItems = lazyPagingItems,
                    onTownClicked = { edge: EdgeParcelable ->
                        val json = Uri.encode(Gson().toJson(edgeParcelable))
                     navController.navigateSingleTopTo("hotspots/$json")
                    },
                    modifier = ...
                )
            }
            composable(
                route = "hotspots/{edge}",
                arguments = listOf( navArgument("edge") {
                        type = NavType.StringType
                    }
                )
            ) {
                val edgeParcelable = Gson().fromJson(Uri.decode(it.arguments?.getString("edge")), EdgeParcelable::class.java)
                HotspotsScreen(edgeParcelable)
            }
        }
    }
}

Then my app worked like a Charm. Sorting this took me like 2 days of trial and error and searching so I hope this can help someone out there if faced with a similar issue...

Answer 10

I had a similar issue where I had to pass a string that contains slashes, and since they are used as separators for deep link arguments I could not do that. Escaping them didn't seem "clean" to me.

I came up with the following workaround, which can be easily tweaked for your case. I rewrote NavHost , NavController.createGraph and NavGraphBuilder.composable from androidx.navigation.compose as follows:

@Composable
fun NavHost(
    navController: NavHostController,
    startDestination: Screen,
    route: String? = null,
    builder: NavGraphBuilder.() -> Unit
) {
    NavHost(navController, remember(route, startDestination, builder) {
        navController.createGraph(startDestination, route, builder)
    })
}

fun NavController.createGraph(
    startDestination: Screen,
    route: String? = null,
    builder: NavGraphBuilder.() -> Unit
) = navigatorProvider.navigation(route?.hashCode() ?: 0, startDestination.hashCode(), builder)

fun NavGraphBuilder.composable(
    screen: Screen,
    content: @Composable (NavBackStackEntry) -> Unit
) {
    addDestination(ComposeNavigator.Destination(provider[ComposeNavigator::class], content).apply {
        id = screen.hashCode()
    })
}

Where Screen is my destination enum

sealed class Screen {
    object Index : Screen()
    object Example : Screen()
}

Please note that I removed deep links and arguments since I am not using them. That will still allow me to pass and retrieve arguments manually, and that functionality can be re-added, I simply didn't need it for my case.

Say I want Example to take a string argument path

const val ARG_PATH = "path"

I then initialise the NavHost like so

NavHost(navController, startDestination = Screen.Index) {
    composable(Screen.Index) { IndexScreen(::navToExample) }

    composable(Screen.Example) { navBackStackEntry ->
        navBackStackEntry.arguments?.getString(ARG_PATH)?.let { path ->
            ExampleScreen(path, ::navToIndex)
        }
    }
}

And this is how I navigate to Example passing path

fun navToExample(path: String) {
    navController.navigate(Screen.Example.hashCode(), Bundle().apply {
        putString(ARG_PATH, path)
    })
}

I am sure that this can be improved, but these were my initial thoughts. To enable deep links, you will need to revert back to using

// composable() and other places
val internalRoute = "android-app://androidx.navigation.compose/$route"
id = internalRoute.hashCode()

Answer 11

Since the nglauber's answer work when going forward and does not when navigating backward and you get a null. I thought maybe at least for the time being we can save the passed argument using remember in our composable and be hopeful that they add the Parcelable argument type to the navigating with the route.

the destination composable target:

composable("yourRout") { backStackEntry ->
                backStackEntry.arguments?.let {
                    val rememberedProject = remember { mutableStateOf<Project?>(null) }
                    val project =
                        navController.previousBackStackEntry?.arguments?.getParcelable(
                            PROJECT_ARGUMENT_KEY
                        ) ?: rememberedProject.value
                    rememberedProject.value = project
                    TargetScreen(
                        project = project ?: throw IllegalArgumentException("parcelable was null"),
                    )
                }

And here's the the source code: to trigger the navigation:

navController.currentBackStackEntry?.arguments =
            Bundle().apply {
                putParcelable(PROJECT_ARGUMENT_KEY, project)
            }
        navController.navigate("yourRout")

Answer 12

A very simple and basic way to do is as below

1.First create the parcelable object that you want to pass eg

@Parcelize
data class User(
    val name: String,
    val phoneNumber:String
) : Parcelable

2.Then in the current composable that you are in eg main screen

 val userDetails = UserDetails(
                            name = "emma",
                             phoneNumber = "1234"
                            )
                        )
navController.currentBackStackEntry?.arguments?.apply {
                            putParcelable("userDetails",userDetails)
                        }
                        navController.navigate(Destination.DetailsScreen.route)

3.Then in the details composable, make sure you pass to it a navcontroller as an parameter eg

@Composable
fun Details (navController:NavController){
val data = remember {
        mutableStateOf(navController.previousBackStackEntry?.arguments?.getParcelable<UserDetails>("userDetails")!!)
    }
}

NB: If the parcelable is not passed into state, you will receive an error when navigating back

Answer 13

My approach with Moshi :

Routes

sealed class Route(
    private val route: String,
    val Key: String = "",
) {
    object Main : Route(route = "main")
    object Profile : Route(route = "profile", Key = "user")

    override fun toString(): String {
        return when {
            Key.isNotEmpty() -> "$route/{$Key}"
            else -> route
        }
    }
}

Extension

import android.net.Uri
import androidx.compose.runtime.Composable
import androidx.compose.runtime.remember
import androidx.core.net.toUri
import androidx.navigation.*
import com.squareup.moshi.Moshi

inline fun <reified T> NavController.navigate(
    route: String,
    data: Pair<String, T>,
    navOptions: NavOptions? = null,
    navigatorExtras: Navigator.Extras? = null,
) {
    val count = route
        .split("{${data.first}}")
        .size
        .dec()

    if (count != 1) {
        throw IllegalArgumentException()
    }

    val out = Moshi.Builder()
        .build()
        .adapter(T::class.java)
        .toJson(data.second)
    val newRoute = route.replace(
        oldValue = "{${data.first}}",
        newValue = Uri.encode(out),
    )

    navigate(
        request = NavDeepLinkRequest.Builder
            .fromUri(NavDestination.createRoute(route = newRoute).toUri())
            .build(),
        navOptions = navOptions,
        navigatorExtras = navigatorExtras,
    )
}

inline fun <reified T> NavBackStackEntry.getData(key: String): T? {
    val data = arguments?.getString(key)

    return when {
        data != null -> Moshi.Builder()
            .build()
            .adapter(T::class.java)
            .fromJson(data)
        else -> null
    }
}

@Composable
inline fun <reified T> NavBackStackEntry.rememberGetData(key: String): T? {
    return remember { getData<T>(key) }
}

Example usage

data class User(
    val id: Int,
    val name: String,
)

@Composable
fun RootNavGraph() {
    val navController = rememberNavController()
    
    NavHost(
        navController = navController,
        startDestination = "${Route.Main}",
    ) {
        composable(
            route = "${Route.Main}",
        ) {
           Button(
              onClick = {
                  navController.navigate(
                      route = "${Route.Profile}",
                      data = Route.Profile.Key to User(id = 1000, name = "John Doe"),
                  )
              },
              content = { Text(text = "Go to Profile") },
        }

        composable(
            route = "${Route.Profile}",
            arguments = listOf(
                navArgument(name = Route.Profile.Key) { type = NavType.StringType },
            ),
        ) { entry ->
            val user = entry.rememberGetData<User>(key = Route.Profile.Key)

            Text(text = "$user")
        }
    }
}

Answer 14

1 - Add the name of the data sent in the route

const val NEWS_DETAILS = "NEWS_DETAILS/{article}/{name}"

2 - Create dataClassParcelable

@Parcelize
data class ArticlesModel(
    @SerializedName("author")
    val author: String?,
    @SerializedName("content")
    val content: String?,
    @SerializedName("description")
    val description: String?,
    @SerializedName("publishedAt")
    val publishedAt: String?,
    @SerializedName("source")
    val source: Strins?,
    @SerializedName("title")
    val title: String?,
    @SerializedName("url")
    val url: String?,
    @SerializedName("urlToImage")
    val urlToImage: String?
):Parcelable

3 - Submit the required data

    fun NavController.openNewsDetails(article: ArticlesModel,name:String) {
        currentBackStackEntry?.savedStateHandle?.apply{

             set(
                 "article",
                 article
             )

             set(
                 "name",
                 name
             )
         }

        navigate(ScreenConst.NEWS_DETAILS)
    }

4 - Reading information and sending them to a new screen

          composable(
                    route = ScreenConst.NEWS_DETAILS
                ) { navBackStackEntry ->
            
                    val article = 
navController.previousBackStackEntry?.savedStateHandle?.get<ArticlesModel("article")
                    val name=
navController.previousBackStackEntry?.savedStateHandle?.get<String>("name")
            
                    if (article==null && name.isNullOrEmpty()) {
                        return@composable
                    }
            
                    DetailsScreen(
                        article = article,
                        name = name
                    )
            
                }